The good people in Lensrentals are it again. Using a combination of tools, expertise and pure moxie, they have broken into one of the most interesting lenses released by Canon in recent memory: the fixed-aperture RF 600mm f / 11 IS STM.
When rumors first surfaced that Canon would be releasing a 600mm f / 11 and 800mm f / 11, many readers were skeptical that these lenses were real. But really they were, and they have generally been well received since they hit the stage. While they will not win awards for optical excellence, they are affordable and get the job done …
Yet the question remains: at what angles does Canon cut to create this interesting optics? Is it just that fixed aperture, or are these lenses built pretty or strangely on the inside? Fortunately, Roger Cicala at Lensrentals decided to open and invent an RF 600mm f / 11 IS STM.
You can read the full lossdown at this link – which includes a quick explanation of Canon’s gapless Diffractive Optics used to enable 2lbd, 600mm lens without breaking the laws of physics – but we will hit on some of the key discoveries below.
First and foremost, although the optical construction is not super complicated (or “a lot of air”), this non-weather magnified lens is actually complex to take apart … which means it will be difficult to repair if things go wrong. On the bright side, it seems that Canon has done a lot to keep the lens rigid and sturdy, despite the largely plastic construction.
Large metal leads are used to hold the expansion mechanism tight, and Canon seems to use an abundance of screws to reinforce the lens anywhere that meets plasticity.
In addition, the lens is electronically quite complex. When she pulled it apart, Roger had to repeatedly break out the alcohol and heat gun to try to clear the labyrinth of flexes that run the entire path from the mountain to the end of the lens barrel. Again: the lens is more complex than you might think.
But the main finding is described by Roger in the conclusion, and if you are not looking for it, you may miss it. It looks like Canon does some fancy, automatic lens adjustment when mounting – something no one else does.
Here is the relevant paragraph (emphasis added):
We found that the electronic construction was complex for a Canon lens, or at least very different. The optical construction at the core has a very Canon look, with various optical adjustments / compensations using its new, large eccentric collars. I remain convinced that this is because Canon makes automated optical adjustment of subgroups during assembly. No one else is adapted to this degree except in this way.
To read the full teardown, learn more about how this lens works, and find out why Roger and the Lensrentals team have no intention of repairing these lenses at home when anything other than the filter ring breaks, head over to the Lensrentals -blog.
Image credits: All photos courtesy of Lensrentals, used with permission.
